java - Android FirebaseDatabase recyclerview 单个变量(userid)的 null 异常

Question

我想显示每个帖子的用户个人资料图片。我为此编写了代码，但出现错误。

//Here is error---

FATAL EXCEPTION: main
Process: com.example.serhat.blog, PID: 5614                                                                           java.lang.NullPointerException: Can't pass null for argument 'pathString' in child() 
at com.google.firebase.database.DatabaseReference.child(Unknown Source)
at com.example.serhat.blog.MainActivity$2.populateViewHolder(MainActivity.java:95)
at com.example.serhat.blog.MainActivity$2.populateViewHolder(MainActivity.java:80)

<小时/>

//Here is my code
 //Profile image//
                mDatabaseUsers.child(model.getUserid()).child("image").addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        String image = dataSnapshot.getValue(String.class);
                        viewHolder.setProfileImage(MainActivity.this,image);
                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {

                    }
                });

//Here is blog class 

    private String title,description,image,uid,username,senddate;


    public Blog()

    {

    }

    public Blog(String title, String description, String image, String uid, String username,String senddate,String profileimageUri) {
        this.title = title;
        this.description = description;
        this.image = image;
        this.uid = uid;
        this.username = username;
        this.senddate=senddate;
    }
    public String getUserid() {
        return uid;
    }
    public void setUserid(String uid) {
        this.uid = uid;
    }

已解决。感谢您的回答。问题是我在 firebase 中的数据库结构，我将“uid”更改为“userid”并解决了问题。

问题是方法名和数据库中的域名不一样。

Answer 1

看起来mDatabaseUsers.child(model.getUserid())中的model.getUserid()是null，这会导致NullPointerException。

用您提供的代码很难判断为什么它为空，但您应该能够调试它。